Polishing film for plastic spectacle lenses

ABSTRACT

A polishing film for a polishing head for plastic spectacle lenses, for polishing zones on a front side or rear side of the spectacle lens, having a polishing surface which can be positioned against the spectacle lens and is bounded by a peripheral surface, wherein an edge is provided between the polishing surface and the peripheral surface, wherein the edge either has a radius r of at least 0.5 mm to 10 mm or has a chamfer f with an extent f1×f2, where the extent f1 or f2 is at least 0.5 mm to 10 mm, or the polishing film, when not in use, has a basic curvature G with a radius RG≧75 mm and, in addition to this, a peripheral curvature G with a radius Rg≦0.5 G, wherein the peripheral curvature g is limited to the peripheral zone, or the polishing film is formed without any basic curvature G and has a peripheral curvature g with a radius Rg≦35 mm, wherein the peripheral curvature g is limited to the peripheral zone.

FIELD OF THE INVENTION

The invention pertains to a polishing film for a polishing head forplastic spectacle lenses for zone polishing of a front or rear side ofthe spectacle lens, with a polishing surface which can be positionedagainst the spectacle lens, being bounded by a peripheral surface, whilean edge is formed between the polishing surface and the peripheralsurface.

Moreover, the invention pertains to a polishing film for a polishinghead for plastic spectacle lenses for zone polishing of a front or rearside of the spectacle lens, with a polishing surface which can bepositioned against the spectacle lens, the polishing surface having aperipheral surface with a width b of at most 0.1 D to 0.3 D or at most0.2 D.

The invention also pertains to a method for producing a polishing filmfor a polishing head for plastic spectacle lenses for zone polishing ofa front or rear side of the spectacle lens, with a polishing surfacewhich can be positioned against the spectacle lens, being bounded by aperipheral surface, while an edge is provided between the polishingsurface and the peripheral surface, wherein the polishing film at thestart of the method is carved out from a web of material, such aspunched out or cut out.

The invention furthermore pertains to a method for producing a polishingfilm for a polishing head for plastic spectacle lenses for zonepolishing of a front or rear side of the spectacle lens, with apolishing surface which can be positioned against the spectacle lens,having a basic diameter D, wherein the polishing film in a first step iscarved out from a web of material, such as punched out or cut out, andthe polishing surface has a peripheral zone with a width b of at most0.1 D to 0.3 D.

BACKGROUND OF THE INVENTION

A polishing head with a polishing film is already known from DE 10 2005010 583 A1. The polishing film is arranged on a foam carrier body andhas a convex basic curvature. In the radial direction, it projects abovethe foam carrier body. According to paragraph [0036], a gap is formedduring the machining of a spectacle lens between the lens and thepolishing film, serving as an annular reservoir of polishing agent.

A polishing head with a polishing film, a carrier layer, and a basicbody is already known from DE 10 2007 026 841 A1. The carrier layer ofthe basic body has a chamfer or recess at the outer circumference sothat the polishing film after being glued fast to the carrier layer isset back in the axial direction on the outer circumference.

SUMMARY OF THE INVENTION

The problem of the invention is to configure and arrange a polishingfilm so that an improved polishing result is assured.

Polishing films, also known as a polishing pad, are punched out or cutout from corresponding webs of material during the manufacture. In thisprocess, a peripheral surface of the polishing film which bounds thepolishing surface is formed, one edge making an angle of around 90° withthe polishing surface itself. In the case of both flat or evenlyconfigured polishing films and convex configured polishing films with abasic curvature G, the polishing film can be positioned against the lenssurface being machined with the entire polishing surface, i.e., up tothe margin or edge. This is especially due to the fact that the elasticcarrier layer which carries the polishing film is fitted to the lenssurface, so that the polishing film lies with its entire surface againstthe spectacle glass. The basic curvature G of the polishing film securedto the polishing head is generally somewhat larger than the curvature ofthe side of the spectacle glass being worked. Therefore, the concavelens surface will at first make contact with the peripheral zone beforethe polishing film is placed fully against the lens surface.

To avoid unwanted polishing effects due to this edge, especially whenusing rather thick polishing films, it is advantageous for the edge tohave a radius r of at least 0.2 mm to 10 mm or 0.5 mm to 3 mm. Theradius r forms a transitional zone z between the polishing surface andthe peripheral surface, preferably passing tangentially into thepolishing surface. Depending on the size of the radius r on the one handand the thickness d of the polishing film on the other hand, differentvalues result for the remaining height h of the peripheral surface. Ifthe radius r runs out to a support surface of the polishing filmarranged opposite the polishing surface, the height h is reduced tozero. A common feature of all designs is that there is no unbroken edgeat the start of the polishing process which might adversely affect thepolishing result.

The radius r or the chamfer f should be chosen so that on the one handthe edge is sufficiently broken and on the other hand the polishing filmdoes not become too thin, or else it will tear more easily.

Polishing films are generally at most 0.5 mm to 3 mm thick. Thethickness d most often used is between 0.8 mm and 2 mm.

The problem is also solved in that the edge has a chamfer f with adimension of f1×f2, where the dimension f1 or f2 is at least 0.2 mm to10 mm or 0.5 mm to 3 mm. The closer the angle which the chamfer f makeswith the polishing surface to the 180° limit, the more constant thetransition between the chamfer f and the polishing surface. In additionto the chamfer f, of course, a radius r can also be worked into saidtransition, so that no edge remains behind at the transition between thechamfer f and the polishing surface. The influence of the chamfer f onthe height h results accordingly.

Moreover, it can be advantageous for the radius r or the chamfer f to beworked into the polishing film by a cutting process or a grindingprocess. The radius r or the chamfer f form a rounding or flattening ofthe edge remaining between the polishing surface and the peripheralsurface after the fabrication process. A cutting process using a millingcutter or a cutting process using a grinding tool can be used for this.

The problem is also solved in that the diameter D1 is: D1=D−2b orD1<D−2b and the polishing film in the unused state prior to being placedagainst a spectacle lens a1) has a basic curvature G with a radiusRG>=70 mm and in addition to this it has a peripheral curvature g with aradius Rg<=0.5 G, Rg<=0.4 G, Rg<=0.3 G, Rg<=0.2 G or Rg<=0.1 G, theperipheral curvature g being confined to the peripheral zone, or a2) thepolishing film is formed with no basic curvature G and it has aperipheral curvature g with a radius Rg<=25 mm, Rg<=15 mm or Rg<=7 mm,the peripheral curvature g being confined to the peripheral zone.

The basic curvature G of the polishing film secured to the polishinghead can be determined by the curvature of a coupling surface of thebasic body of the polishing head, since the curvature of the basic bodyis transferred to the elastic carrier layer. But the elastic carrierlayer only partly transfers this curvature to the polishing film, sothat the basic curvature G of the fastened polishing film is somewhatlarger, i.e., it has a somewhat larger radius than the curvature of thebasic body. The polishing film can also itself have the basic curvatureG thanks to a corresponding manufacturing or machining process. In thecase without basic curvature G, neither the polishing film nor the basicbody or the carrier layer has a curvature.

Thanks to the use of a peripheral curvature g, the edge between thepolishing surface and the peripheral surface is sufficiently distancedfrom the lens surface being polished. A detrimental influence on thepolishing results is prevented. Especially when the polishing film isunused, said edge is relatively stiff, so that detrimental influencesmight be produced.

The elastic carrier layer is generally made of foam material and formsthe connecting element to the coupling surface of a basic body G of apolishing head. If the elastic carrier layer is secured to the basicbody, the polishing head so formed can be used with the polishing filmsecured to the carrier layer. The fastening of the polishing filmgenerally occurs via a glue connection or by vulcanization or a hook andeye closure.

It can be advantageous for the peripheral curvature g to be limited to amaximum of 10% or 50% of the peripheral zone. Hence, the polishing filmprojects radially beyond the carrier layer by more than the peripheralzone. This projection U has no curvature, or only the basic curvature G.

The problem is also solved by a polishing head with a polishing film, asdescribed above, which is suitable for zone polishing of a plasticspectacle lens. This suitability is due to the fact that the carrierlayer is elastically configured and the polishing head or the carrierlayer with the polishing film is smaller by a diameter of around 45 mmthan a spectacle lens or semifinished product being machined. Thediameter of a spectacle lens being machined is on average 60 mm to 85mm. In this case, an edge machining has not yet been done for thespectacle lens being polished.

The method according to the invention involves feeding the polishingfilm to a cutting tool, such as a cup-shaped grinding tool or a millinghead, and breaking the edge by the cutting tool. The edge after thispreferably has a radius r and/or a chamfer f of at least 0.2 mm to 10 mmor 0.5 mm to 5 mm. This occurs independently of a basic curvature G ofthe polishing film.

The additional method according to the invention involves providing thepolishing film with a basic curvature G with a radius RG>=70 mm and inaddition to this providing an extra peripheral curvature g in a shapingprocess, i.e., by application of a shaping tool in the peripheral zone ,prior to the use for a spectacle lens being manufactured, with Rg<=0.5G, Rg<=0.4 G, Rg<=0.3 G, Rg<=0.2 G, or Rg<=0.1 G, or configuring thepolishing film without a basic curvature G, i.e., flat or level, andproviding a peripheral curvature g located exclusively in the peripheralzone in a shaping process prior to the use for a spectacle lens beingmanufactured. Preferably, a peripheral curvature g is used with a radiusRg<=35 mm, Rg<=25 mm, Rg<=15 mm or Rg<=7 mm. The peripheral curvatureproduces a peripheral region of the polishing film at a distance fromthe lens surface. The peripheral curvature g can also be chosen to bevery small with increasing distance from the peripheral surface, sincethe transition between the projecting peripheral region of the polishingfilm and the polishing surface of the polishing film making contact withit is sufficiently constant.

The basic curvature G is accomplished by fastening the naturally flat orlevel polishing film to an elastic carrier layer partly reflecting theconvex shape of the basic body. The carrier layer itself is a hollowcylinder, with no curvature at the contact zone or at the top or bottomside. Alternatively, the basic curvature G can also be an intrinsic partof the polishing film, i.e., generated in a corresponding manufacturingor machining process of the polishing film.

Furthermore, it can be advantageous for the breaking of the edge or themolding of the peripheral curvature g to occur after the fastening onthe carrier layer, wherein the polishing film is guided or supportedindirectly by the carrier layer when machining the edge. The carrierlayer can generally be secured already to a basic body of a polishinghead, serving to hold the polishing head in a tool spindle for themachining of the polishing film.

The polishing film can also be machined basically before the fasteningonto the carrier layer and for this it is placed in a separate workpieceholder.

The molding of the peripheral curvature g can also be done by a moldingprocess with the use of heat and/or pressure. This depends primarily onthe material properties of the polishing film.

The problem is also solved in that a structurized material web isproduced before carving out the polishing film, which has severalformations whose shape corresponds to a polishing film with a peripheralcurvature g arranged in the peripheral zone, and in that the carving outof the respective formation produces a polishing film with a peripheralcurvature g situated in the peripheral zone. Since it is not easilypossible to mold the peripheral curvature g, especially in the case ofmaterials like duopolistic, a molding of the peripheral curvature gduring the generic manufacturing process of the corresponding film ormaterial web is advantageous. The material web is provided withcorresponding troughlike formations or indentations during thefabrication, having the geometry of the ultimately desired polishingfilm with peripheral curvature g. The formations or indentations are cutout or punched out from the material web produced in this way.

BRIEF DESCRIPTION OF THE DRAWINGS

Further benefits and features of the invention are explained in thepatent claims and in the specification and represented in the figures.There are shown:

FIG. 1, a sectional representation of a polishing head with variousdetail views;

FIG. 1 a, another detail view,

FIG. 2 a, 2 b, a perspective diagram of a material web of the film.

DETAILED DESCRIPTION OF THE INVENTION

According to FIG. 1, the polishing head 2 has a basic body 2.2 forseating in a polishing spindle (not shown), an elastic carrier layer 2.1fastened on the basic body 2.2 and a polishing film 1 fastened on theelastic carrier layer 2.1. The basic body 2.2 has a concavely shapedcoupling surface 2.3, on which the carrier layer 2.1 is secured. Theelastic carrier layer 2.1 has a contact zone 2.4, on which the polishingfilm 1 is secured. The contact zone 2.4 and therefore the polishing film1 are likewise concavely shaped, according to the coupling surface 2.3.The polishing film 1 has a basic diameter D, which is around 15% largerby a width b than a basic diameter D′ of the carrier layer 2.1.Therefore, a radial projection of the polishing film 1 results, whoseconfiguration shall be described hereafter by means of the detail viewsD1, D2 and D3, as well as FIG. 1 b. The elastic carrier layer 2.1 has aconvex top side, following the shape of the coupling surface 2.3 of thebasic body 2.2, with a basic curvature G, whose radius of curvaturethanks to the elasticity of the carrier layer 2.1 is somewhat largerthan that of the coupling surface 2.3.

According to detail view D1, the polishing film 1 has a peripheral zone1.4, which extends for a width b, which corresponds to 5% of thediameter D of the polishing film 1. Within this peripheral zone 1.4, aperipheral curvature g is formed on the polishing film 1, which differsin size from the basic curvature G.

The peripheral curvature g is superimposed on the basic curvature G. Thepolishing film 1 has a polishing surface 1.1 which can be placed againstthe spectacle lens 3, which according to detail view D1 runs radiallyoutward across the peripheral zone 1.4 as far as one edge 1.3. The edge1.3 constitutes the boundary between the polishing surface 1.1 and aperipheral surface 1.2 adjoining the polishing surface 1.1. Thanks tothe shaping of the peripheral curvature g, the edge 1.3 is given asufficiently large distance from a rear side 3.2 of a plastic spectaclelens 3 which can be placed against the polishing surface 1.1 accordingto the basic curvature G. Thus, the plastic spectacle lens 3 does notcome into contact with the edge 1.3 and at least a part of theperipheral zone 1.4.

The peripheral surface 1.2 in the region of the edge 1.3 makes an angleof around 90° with the polishing surface 1.1. This geometry results fromthe punching out process of the polishing film 1 from a material webforming the polishing film 1 by means of a cup-shaped punching tool.

According to detail view D2, the polishing film 1 has a radius r in theregion of the edge 1.3 so that the former edge 1.3 is broken. Thanks tothe radius r, a transitional zone z is formed between the peripheralsurface 1.2 and the polishing surface 1.1, which runs tangentially intothe polishing surface 1.1. Depending on a thickness d of the polishingfilm 1 on the one hand and the chosen radius r on the other hand, aremaining height h is produced for the peripheral surface 1.2, which ispreferably not larger than 50% of the thickness d. Thanks to the formingof the radius r, it is not necessary to form a peripheral curvature g,as shown in detail view D1. Even so, both the peripheral curvature g andthe radius r can also be provided.

According to detail view D3, as an alternative to the radius r describedin detail view D2 there is provided a chamfer f on the edge 1.3. Thechamfer f has the dimensions f1, f2. The two dimensions f1, f2 arechosen such that a transition between the chamfer f and the polishingsurface 1.1 is as smooth as possible. In keeping with the remarks on theradius r, a remaining height h of the peripheral surface 1.2 results,depending on the particular dimensions f1, f2 for the chamfer f on theone hand and the thickness d of the polishing film 1 on the other hand.

The polishing head 2 can be positioned with the polishing film 1 againsta plastic spectacle lens 3 or a rear side of the spectacle lens 3 forthe purpose of polishing the rear side 3.2. Depending on the plasticspectacle lens 3 or plastic spectacle lens semifinished product used,the polishing head 2 will in addition or alternatively to the rear side3.2 of the spectacle lens 3 also polish a front side 3.1 of thespectacle lens 3.

For the purpose of forming the radius r or the chamfer f, the use of acutting tool is provided, such as a grinding tool or a milling cutter.The forming of the peripheral curvature g is done by the use of anappropriate mold.

According to FIG. 1 a, the radius r is chosen such that the polishingfilm 1 runs out to a point at the edge 1.6. The radius r makes an angleα of around 40° with a supporting surface 1.5 lying opposite thepolishing surface 1.1. At the edge 1.6, the angle α subtended betweenthe radius r or the chamfer f and the supporting surface 1.5 should notbe less than 30°, so that the polishing film 1 does not tear.

According to FIG. 2 a, 2 b, the structurized material web 4 of thepolishing film 1 has several formations 4.1, 4.1′, whose shapecorresponds to a polishing film 1 with a peripheral curvature g situatedin the peripheral zone 1.4. According to FIG. 2 a, the formation 4.1 isconfigured to be upwardly projecting, while according to FIG. 2 b theformation 4.1 is downward projecting. By cutting or punching along theperipheral line, the respective formation 4.1 is carved out and thus oneobtains a polishing film 1 with a peripheral curvature g situated in theperipheral zone 1.4, such as is secured on the carrier layer accordingto detail view D1. The polishing film 1 shown here has no basiccurvature G. It is given such curvature by being fastened to the convexshaped elastic carrier layer 2.1.

LIST OF REFERENCE SYMBOLS

-   1 polishing film-   1.1 polishing surface-   1.2 peripheral surface-   1.3 edge-   1.4 peripheral zone-   1.5 support surface-   1.6 edge-   2 polishing head-   2.1 elastic carrier layer, carrier layer-   2.2 basic body-   2.3 coupling surface-   2.4 contact zone-   3 plastic spectacle lens, spectacle lens-   3.1 front side-   3.2 rear side-   4 material web-   4.1 formations-   4.1′ formations-   b width-   D basic diameter-   D′ basic diameter-   d diameter of 1-   f chamfer-   f1 dimension-   f2 dimension-   G basic curvature-   g peripheral curvature-   h height of 1.2-   r radius of 1.3-   RG radius of the basic curvature-   Fg radius of the peripheral curvature-   U projection-   z transition zone-   α angle

What is claimed is:
 1. A polishing film for a polishing head for plastic spectacle lenses for zone polishing of a front side or rear side of the spectacle lens, comprising: a polishing surface which can be positioned against the spectacle lens, being bounded by a peripheral surface, while an edge is formed between the polishing surface and the peripheral surface, wherein the edge has a radius r of at least 0.2 mm to 10 mm.
 2. A polishing film for a polishing head for plastic spectacle lenses for zone polishing of a front side or rear side of the spectacle lens, comprising: a polishing surface which can be positioned against the spectacle lens, being bounded by a peripheral surface, while an edge is formed between the polishing surface and the peripheral surface, wherein the edge has a chamfer f with a dimension of f1×f2, where the dimension f1 or f2 is at least 0.2 mm to 10 mm.
 3. The polishing film according to claim 1, wherein the radius r is worked into the polishing film by a cutting process or a grinding process.
 4. A polishing film for a polishing head for plastic spectacle lenses for zone polishing of a front side or rear side of the spectacle lens, comprising: a polishing surface which can be positioned against the spectacle lens, having a basic diameter D, wherein the polishing film is secured to an elastic carrier layer with a diameter D1 and the polishing surface has a peripheral zone with a width b of at most 0.1 D to 0.3 D, wherein the diameter D1 is: D1=D−2b or D1<D−2b and the polishing film in the unused state prior to being placed against a spectacle lens a1) has a basic curvature G with a radius RG>=70 mm and in addition to this it has a peripheral curvature g with a radius Rg<=0.5 G, the peripheral curvature g being confined to the peripheral zone, or a2) the polishing film is formed with no basic curvature G and it has a peripheral curvature g with a radius Rg<=35 mm, the peripheral curvature g being confined to the peripheral zone.
 5. The polishing film according to claim 4, wherein the peripheral curvature g is limited to a maximum of 10% of the peripheral zone.
 6. A polishing head with a polishing film according to claim 1 for zone polishing of a spectacle lens.
 7. A method for producing a polishing film for a polishing head for plastic spectacle lenses for zone polishing of a front side or rear side of the spectacle lens, with a polishing surface which can be positioned against the spectacle lens, being bounded by a peripheral surface, while an edge is formed between the polishing surface and the peripheral surface, comprising the steps of: a) carving the polishing film out from a web of material, b) bringing the polishing film up to a cutting tool and the edge is broken off by the cutting tool.
 8. A method for producing a polishing film for a polishing head for plastic spectacle lenses for zone polishing of a front side or rear side of the spectacle lens, with a polishing surface which can be positioned against the spectacle lens, having a basic diameter D, comprising the steps of: a) carving the polishing film out from a web of material, wherein the polishing surface has a peripheral zone with a width of at most 0.3 D, b1) providing the polishing film with a basic curvature G, with G>=70 mm, and in addition to this it is provided with an extra peripheral curvature g in a shaping process in the peripheral zone, prior to the use for a spectacle lens being manufactured, with a radius Rg<=0.5 G, or b2) configuring the polishing film without a basic curvature G, and it is provided with a peripheral curvature g located exclusively in the peripheral zone in a shaping process prior to the use for a spectacle lens being manufactured.
 9. The method for producing a polishing head with a polishing film according to claim 7, wherein the polishing film is secured to an elastic carrier layer of a polishing head, wherein the breaking of the edge occurs after the fastening on the carrier layer, wherein the polishing film is guided or supported indirectly by the carrier layer when machining the edge.
 10. A method for producing a polishing film for a polishing head for plastic spectacle lenses for zone polishing of a front side or rear side of the spectacle lens, with a polishing surface which can be positioned against the spectacle lens, having a basic diameter D, wherein the polishing surface has a peripheral zone with a width of at most 0.3 D, comprising the steps of: a) carving several polishing films out from a material web, producing a structurized material web before step a), which has several formations whose shape corresponds to a polishing film with a peripheral curvature g arranged in the peripheral zone, and wherein the carving out of the polishing film from the structurized material web at the periphery of the respective formation produces a polishing film with a peripheral curvature g situated in the peripheral zone.
 11. The polishing film according to claim 2, wherein the chamfer f is worked into the polishing film by a cutting process or a grinding process.
 12. A polishing head with a polishing film according to claim 2 for zone polishing of a spectacle lens.
 13. A polishing head with a polishing film according to claim 4 for zone polishing of a spectacle lens.
 14. The method for producing a polishing head with a polishing film according to claim 8, wherein the polishing film is secured to an elastic carrier layer of a polishing head, wherein the molding of the peripheral curvature g occurs after the fastening on the carrier layer, wherein the polishing film is guided or supported indirectly by the carrier layer when machining the edge. 